This invention relates to a method and apparatus for assembling a structure composing of a vehicle body and the like, such as roof structure, side structure or end structure of a rolling stocks or other vehicles.
Common roof structures of rolling stocks comprise a roof framing which consists of carlings 1, stringers 2 and cant rails 3, and roof sheets 4 spread thereon, as shown in FIG. 1.
A typical conventional assembling method of vehicle roof structures thus arranged can be explained as follows:
Carlings 1 are placed on positioners previously spaced at given frame intervals on a jig, clamped with hand vises, and welded to stringers 2, thus making a one-piece roof framing. The integrated roof framing is removed from the jig, turned over with a crane and other handling devices, and placed on a stand for welding the back side of the framing to complete the assembly of the roof framing. After roof sheets 4 are placed upside down on a roof-sheet stand, the aforesaid framing is mounted on the roof sheets and tack welded to the sheets into one piece, which is tranferred to a welding stand to secure it. Then the framing and roof sheets are spot welded to complete this type of roof structure.
Finally the roof structure A is turned over with a crane or other handling devices and combined with side structures 10 and end structures 11, completing a vehicle's body as shown in FIG. 2.
In the course of the manufacturing process mentioned above, the roof structure A is turned over twice. The turnover operation is performed by slinging one side end of a roof structure with an overhead crane, lifting the end upright in a sling, two workers holding both ends of the roof structure, and by turning over the roof structure by crane operation along with manipulation by the two workers.
However, the aforesaid turn-over operation of a roof structure has the following problems:
(a) One or two overhead cranes are required for turning over a roof structure;
(b) The availability of overhead cranes may affect this work's efficiency because idle queueing time may take place if necessary cranes are being occupied with other jobs;
(c) A total of three or four men, that is one or two crane operators and two workers on the floor (including one who gives signals), is required;
(d) Turning over a roof structure needs a working area at least roughly twice that of the roof structure itself;
(e) Lift-up operation may cause deflections and scars on a roof structure, thus resulting in quality control problems;
(f) A roof structure consisting only of roof sheets and carlings without stringers, for instance, cannot be turned over because of the small resistance to deflection and torsion; and
(g) In hoisting a roof structure with one overhead crane, the left and right sides of the roof structure may tend to hang unsynchronously poised because of the unbalance of the weight, thus causing safety problems.